Bearing liner

ABSTRACT

To provide support for a rotatable shaft, a bearing ball is fixed to the shaft and rotatably mounted within a bearing race. A low friction liner which is disposed between the wearing surfaces of the ball and the race includes a backing, which can be adhered to the wearing surface of the bearing race, and a layer of low friction material, which can be disposed to contact the bearing and thereby provide permanent lubrication between the bearing and the race. The backing can be paper impregnated with chopped, compressed fibers such as wood or rice to provide the liner with a substantially linear stress-strain characteristic similar to that of metals. The paper backing reduces the deflection of the liner in response to compressive stresses so that the accuracy of movement of the bearing within the race is increased significantly. The layer of low friction material may be formed from an intimate mixture of an adhesive and small particles of a low friction material.

United States Patent [1 1 Turner Aug. 19, 1975 1 1 BEARING LINER PrimaryExaminer-George F. Lesmes Assistant Examiner.lames .1. Bell 1 t Pt H.T Bb' k,C'lf.

[75] nven or 6 er umer ur an d 1 Attorney, Agent, or FirmEllsworth R.Roston [73] Assignee: Sargent Industries, Inc., Los

Angeles, Calif. ABSTRACT [22] Flled: June 1974 To provide support for arotatable shaft, a bearing ball [21] App]. No: 475,622 is fixed to theshaft and rotatably mounted within a Related [15. Application Databearing race. A low friction liner which is disposed between the wearingsurfaces of the ball and the race includes a backing, which can beadhered to the wearing surface of the bearing race, and a layer of lowfriction material, which can be disposed to contact the bearing andthereby provide permanznt lubrication between the bearing and the race.The backing can be paper impregnated with chopped, compressed fiberssuch as wood or rice to provide the liner with a substantially linearstress-strain characteristic similar to that of metals. The paperbacking reduces the deflection of the liner in response to compressivestresses so that the accuracy of movement of the bearing within the raceis increased significantly. The layer of low friction material may beformed from an intimate mixture of an adhesive and small particles of alow friction material.

23 Claims, 4 Drawing Figures BEARING LINER This is a continuation ofapplication Ser. No. 274,606, filed July 24, I972 now abandoned.

BACKGROUND OF THE INVENTION 1. Field of the Invention This inventionrelates generally to low friction liners for reducing the frictionbetween wearing surfaces, and more specifically to bearing liners foruse between bearing balls and bearing races.

2. Description of the Prior Art Bearing liners have been disposedbetween bearings and bearing races to reduce the friction forces createdby their wearing surfaces. One of the most recent advances in thebearing liner art is the disclosure by Peter H. Turner in US. Pat. No.3,594,049, of a backing member coated on one side with a layer ofadhesive and coated on the opposite side with an intimate mixture ofadhesive and small particles of a low friction material. The adhesivelayer provides a means for bonding the backing member to one of thewearing surfaces, and the low friction layer provides a means forpermanently lubricating the wearing surfaces. In U.S. Pat. No.3,594,049, the backing member is disclosed in one embodiment to comprisea woven sheet formed from dacron or nylon strands. Such a bearing linerprovides a significant advance over the prior art especially withrespect to its reduced thickness and the considerably increased durationof its useful life.

SUMMARY OF THE INVENTION The present invention includes a backing memberhaving an adhesive layer on one side thereof and an intimate mixture ofan adhesive and a low friction material on the opposite side thereof.The backing member can be an unwoven material impregnated with randomlydisposed compressed fibers such as vegetable fibers to provide thebearing liners with stress-strain characteristics which aresubstantially linear regardless of the compressive stress imposed uponthe backing member. The deflection of the improved liners in response toa particular value of compression is accordingly minimized. Thischaracteristic is particularly advantageous in improving the accuracy ofmovement of the bearings within the bearing liners.

The surfaces of the backing member can be calendered or smoothed toharden the backingmember and to enable the layer including the lowfriction material to be fabricated with a substantially constantthickness. A low friction layer with a substantially constant thicknesswill have a longer useful life since there will be no thin spots to wearthrough and end prematurely the life of the liner.

The backing member also can comprise a laminate including layers offiber-impregnated material wherein the fibers in each layer are alignedsubstantially perpendicular to those in adjacent layers. The resultingbearing liners have a modulus of elasticity which is similar to that ofmetals. The improved liners have characteristics including high tensilestrength and compressive rigidity to extend their useful life andimprove the accuracy of movement of the bearing balls within theirraces.

DESCRIPTION OF THE DRAWINGS FIG. 1 is a side elevational view partiallyin section of a shaft supported by a bearing ball and a bearing racewith a bearing liner disposed between the ball and the race;

FIG. 2 is a side elevational view in cross section of one embodiment ofthe bearing liner;

FIG. 3 is a perspective view of a further embodiment of the bearingliner; and g FIG. 4 illustrates curves representing bearing linercompression versus bearing liner deflection for the bearing liners ofthe prior art and the improved bearing liners.

DESCRIPTION OF PREFERRED EMBODIMENTS Referring to the drawings and inparticular to FIG. 1 thereof, reference numeral 11 designates arotatable shaft on which is mounted a bearing ball 13 having an outer orwearing surface 15. A bearing race 17 having an inner or wearing surface19 can be centered upon the ball 13 to provide support for the shaft 1l. A bearing liner 21 is preferably disposed between the wearing surface19 of the race 17 and the wearing surface 15 of the ball 13. Thusdisposed the bearing liner 21 can provide a means for permanentlylubricating the bearing 13 and the race 17 so that there is lessresistance to relfriction layer 31 can be disposed upon the second majorsurface 27. The low friction layer 31 is partially defined by a wearingsurface 33.

In the preferred embodiment the backing 23 is adhered to the wearingsurface 19 of the race 17 by the adhesive layer 29. Thus disposed theliner 21 has a fixed relationship with the bearing race 17, and thewearing surface 33 of the low friction layer 31 slidably engages thewearing surface 15 of the ball 13. It can be appreciated by thoseskilled in the art that the bearing liner 2] may be adhered to the ball13 in which case the wearing surface 33 would be in contact with thewearing surface 19.

The adhesive comprising the adhesive layer 29 can be any of thoseadhesives disclosed by Peter H. Turner in US. Pat. No. 3,594,049 andassigned of record to the assignee of record of the present application.One such adhesive is Rabond R-840l5 produced by Raybestos-Manhattan ofBridgeport, Connecticut.

The low friction layer 31 can comprise a similar adhesive filled with aS-micron polytetrafluoroethylene powder manufactured by DuPont. Theadhesive and the powder can be intimately mixed in the proportionsdisclosed in US. Pat. No. 3,594,049; however, lower ratios of powder toadhesive are preferred since the compressed fibers in the backing have atendency to absorb some of the adhesive from the wear coating mixture.For example, the low friction powder may have a range of approximately20 percent to 35 percent by weight with the remainder being adhesive. Inthe preferred embodiment the low friction layer contains 20 percent byweight of polytetrafluoroethylene powder. The low friction layer mayhave a thickness of approximately 0.003 inch beyond the peaks of thebacking layer 23. eferably this dimension is no greater thanapproximately 0.0035 inch.

The backing 23 can comprise a fibrous material such as paper havingfibers such as those shown generally at 35. In one of the embodimentsthe fibers 35 are chopped and randomly disposed within the backing 23.The fibers 35 are preferably compressed since a minimum porosity isdesirable to augment the adhesion of the adhesive and low frictionlayers 29 and 31, respectively, to the backing 23. It should beunderstood that the randonly disposed fibers 35 can comprise any fiberalthough the compressed vegetable fibers commonly available in the formof paper are particularly advantageous and economically desirableCalendered paper and rice paper contain fibers which are some of themost compressed and therefore provide excellent deflectioncharacteristics.

Since the backing 23 is a fibrous material, the particles of powder canbe retained between the fibers to provide a mechanical bond between thefibers and the particles of low friction material. This is particularlydesirable since the particles are quite small. A chemical bond also canbe produced between the adhesive and the particles of low frictionmaterial. Furthermore, by compressing the backing 23, the thickness ofthe backing is maintained substantially constant so that the thicknessof the layer 31 of the adhesive and the low friction material will besubstantially constant. This will insure that there will be no thinspots in the low friction layer to wear prematurely and end the usefullife of the liner 21.

The layer 31 has all of the advantages disclosed in US. Pat. No.3,594,049. For example, it has a long life. This results in part fromthe thin dimensions of the layer 31 and in part from the combination ofthe me- 'chanical and chemical bonding of the particles of low frictionmaterial. It also results in part from the small size of the particlesof low friction material. All of these advantages tend to prevent thelow friction material from forming into a continuous smear on theexposed surface of the layer 31.

A further embodiment of the backing 23 is shown in FIG. 3. In thisbacking a plurality of layers such as layers 37, 39, and 41, are adheredto each other to form a laminate. Each of the layers 37, 39, and 41includes fibers 43, 45, and 47, respectively, oriented in a singledirection so that the tensile strength of the layer is in creased inthat direction. In the preferred embodiment each layer, such as thelayer 39, is disposed with respect to the layers on either side thereof,such as the layers 37 and 41, so that its fibers are substantialllynormal to the fibers in the adjacent layers. It follows that thedirection of orientation of the fibers 43 and 47 in the layers 37 and41, respectively, may be substantially parallel. The laminate shown inFIG. 3 provides the backing 23 with increased tensile strength andsubstantially uniform stress properties. This increased strength can beadvantageous in those applications wherein a higher degree of linerreinforcement is desirable.

It is apparent that the bearing liners 21 will be subjected tocompressive forces as the shaft 11 and the ball 13 rotate. It can beappreciated that any deflection of the bearing liners in response tothese compressive forces will increase the wear on the engaging surfacesand reduce the accuracy of thelshaft rotation. Bearing liners includingwoven materials, such as dacron, as disclosed in US. Pat. No. 3,594,049,have represented a significant advance over the prior art. Assatisfactory as the bearing liners disclosed in US. Pat. No. 3,594,049

have been found to be, it is always desirable to provide bearing linerswith enhanced characteristics such as enhanced deflectioncharacteristics.

The stress-strain curve shown in FIG. 4 and designated by the referencenumeral 49 is characteristic for the bearing liners disclosed in US.Pat. No. 3,594,049. For comparison, a stress-strain curve 51characteristic of the improved liners 21 is also shown in FIG. 4. Thecurve 51 has a yield point 53 beyond which the liner will deflect withprogressively decreased increments in load. It will be noted that thedeflection is substantially linear in the regions of compressive forcebelow the yield point 53, where the effects of the bearing liner 21 aremost significant, It is apparent also that, for a given compressiveforce, the deflection is less in the liners 21 comprising the compressedfiber backing 23 than in the liners comprising the backings of the priorart. In fact, the backing 23 provides the liner 21 with a modulus ofelasticity which is similar to that for metals in that the stress-straincurve 51 is substantially linear for values of compressionless than thatat the yield point 53.

It can be seen that the bearing liners 21 including the improved backing23 have particularly advantageous properties for reducing thecoefficient of friction between the wearing surfaces 15 and 19 withoutsignificantly reducing the compressive strength of the materialsupporting the ball 13. Thus, the bearing liner 21 provides a means forpermanently lubricating the ball 13 without sacrificing the accuracy ofmovement and stability of the shaft ,11. This accuracy of movement canhave particular significance in systems which incorporateservomechanisms for amplifying mechanical movement. It is apparent that,in these systems, even a slight deflection of the shaft 11 can beamplified to ultimately produce a substantial error in movement. Thus,the low deflection characteristics of the backing 23 significantlydecrease the error associated with these systems. Furthermore, theresulting bearing liners 21 also have increased rigidity and improvedwear life characteristics.

While the present invention has been shown and described in whatare'eonceived to be the most practical and preferred embodiments, it isrecognized that departures may be made therefrom within the scope of theinvention, which is therefore not to be limited to the details disclosedherein.

I claim:

1. A liner for reducing the coefficient of friction between first andsecond surfaces movable relative to each other, comprising:

a fibrous backing having first and second major surfaces and havingchopped and compressed fibers to reinforce the liner;

an adhesive layer in fixed relationship with the first major surface ofthe backing for bonding the backing to the first surface; and I a lowfriction layer in fixed relationship with the second major surface ofthe backing and providing a low friction surface for slidably engagingthe second surface, the low friction layer having a thin dimensionrelative to the second major surface and being formed from smallportions of low friction material interspersed in an adhesive; wherebythe second and low friction surfaces have a lower coefficient offriction than the first and second surfaces.

2. The low friction linear as defined in claim 1 wherein the compressedfibers are randomly disposed in the backing.

3. The low friction liner as defined in claim 1 wherein the low frictionlayer comprises an intimate mixture of an adhesive and a powder of a lowfriction material.

4. The low friction liner recited in claim 1 wherein the fibrous backingcomprises paper and the compressed fibers are vegetable fibers.

5. The low friction liner as defined in claim 1 wherein the fibrouspaper backing is calendered to harden the surfaces of the backing.

6. The low friction layer as defined in claim 1 wherein the fibrousbacking is a laminate comprising:

a first layer of fibers generally oriented to provide a relatively hightensile strength in a first direction, and

at least a second layer of fibers similar to the first layer anddisposed in surface contact therewith and generally oriented in a seconddirection transverse to the first direction; whereby the laminatedbacking provides the liner with properties including a high tensilestrength and substantially improved stress properties.

7. A bearing liner for use between a first surface and a second surfacefor reducing the friction between the first and second surfaces duringrelative movement between the first and second surfaces, comprising:

first means constituting a fibrous material and having first and secondmajor surfaces for reinforcing the liner, the first means havingcharacteristics providing a deflection in response to a givencompressive force;

second means for adhering the first major surface of the first means tothe second surface; and

third means constituting particles of a low friction material in amechanically bonded relationship with the fibrous material constitutingthe first means and providing a low friction layer between the firstmeans and the first surface, the third means including an adhesive.

8. The bearing liner as defined in claim 7, wherein fibers are disposedat random within the fibrous material.

9. The bearing liner as defined in claim 8 wherein the third meansincludes an intimate mixture of an adhesive and the particles of the lowfriction material constitute a powder.

10. The bearing liner as recited in claim 9 wherein the fiber is avegetable fiber and the deflection of the liner is substantialy directlyproportional to the applied compressive force.

11. The bearing liner as defined in claim 10 wherein the vegetablefibers are compressed.

12. The bearing liner as defined in claim 10 wherein the vegetablefibers includes rice.

13. The bearing liner as defined in claim 9 wherein the first means isformed from at least a pair of laminations and wherein the fibers areoriented in a first one of the laminations to provide a relatively hightensile strength in a first direction and wherein the fibers areoriented in a second one of the laminations to provide a relatively hightensile strength in a second direction transverse to the firstdirection.

14. The liner set forth in claim 1 wherein the low friction layerextends above the second major surface by a dimension no greater thanapproximately 0.0035 inches.

15. The liner set forth in claim 1 wherein the particles of low frictionmaterial have a thickness no greater than 5 microns and wherein theparticles of low friction material are retained between the fibers ofthe fibrous backing.

16. The liner set forth in claim 15 wherein the particles of lowfriction material constitute a polytetrafluoroethylene and wherein thepolytetrafluoroethylene constitutes approximately 20 percent to 35percent of the low friction layer by weight with the remainderconstituting the adhesive.

17. The liner set forth in claim 16 wherein the adhesive in the adhesivelayer and the adhesive in the low friction layer are the same andwherein the low friction layer extends above the second major surface bya distance no greater than approximately 0.0035 inches.

18. A hearing liner as set forth in claiam 8 wherein the fibers in thefibrous material are compressed.

19. A bearing liner as set forth in claim 18 wherein the third meansconstitutes an intimate mixture of an adhesive and the particles of thelow friction material and wherein the low friction material constitutesa polytetrafluoroethylene.

20. The bearing liner set forth in claim 7, wherein the first meansincludes fibers disposed within the fibrous material and wherein thefirst means provides a relatively small amount of deflection whensubjected to different compressive forces and further providessubstantially a linear'relationship between progressive amounts ofprogressive forces imposed upon the first means and the deflectionproduced in the first means by such progressive forces.

21. The bearing liner set forth in claim 20 wherein the first meanscomprises a pair of attached laminations each formed from a fibrousmaterial with one of the layers having fibers disposed in a firstorientation and the other layer having fibers disposed in a secondorientation different from the first orientation.

22. The bearing liner set forth in claim 1 wherein the fibrous backingis disposed in layers and wherein the compressed fibers have a firstorientation in one of the layers and have in a second one of the layersa second orientation different from the first orientation.

23. The bearing liner set forth in claim 7 wherein the first meansconstitutes at least a pair of layers of the fibrous material andwherein fibers are disposed in a first orientation in one of the layersand wherein fibers are disposed in a second one of the layers in asecond orientation different from the first orientation.

1. A LINER FOR REDUCING THE COEFFICIENT OF FRICTION BETWEEN FIRST ANDSECOND SURFACES RELATIVE TO EACH OTHER, COMPRISING: A FIBROUS BACKINGHAVING FIRST AND SECOND MAJOR SURFACES AND HAVING CHOPPED AND COMPRESSEDFIBERS TO REINFORCE THE LINER, AN ADHESIVE LAYER IN FIXED RELATIONSHIPWITH THE FIRST MAJOR SURFACE OF THE BACKING FOR BONDING THE BACKING TOTHE FIRST SURFACE, AND A LOW FRICTION LAYER IN FIXED RELATIONSHIP WITHTHE SECOND MAJOR SURFACE OF THE BACKING AND PROVIDING A LOW FRICTIONSURFACE FOR SLIDABLY ENGAGING THE SECOND SURFACE, THE LOW FRICTION LAYERHAVING A THIN DIMENSION RELATIVE TO THE SECOND MAJOR SURFACE AND BEINGFORMED FROM SMALL PORTIONS OF LOW FRICTION MATERIAL INTERSPERSED IN ANADHESIVE WHEREBY THE SECOND AND LOW FRICTION SURFACES HAVE A LOWERCOEFFICIENT OF FRICTION THAN THE FIRST AND SECOND SURFACES.
 2. The lowfriction linear as defined in claim 1 wherein the compressed fibers arerandomly disposed in the backing.
 3. The low friction liner as definedin claim 1 wherein the low friction layer comprises an intimate mixtureof an adhesive and a powder of a low friction material.
 4. The lowfriction liner recited in claim 1 wherein the fibrous backing comprisespaper and the compressed fibers are vegetable fibers.
 5. The lowfriction liner as defined in claim 1 wherein the fibrous paper backingis calendered to harden the surfaces of the backing.
 6. The low frictionlayer as defined in claim 1 wherein the fibrous backing is a laminatecomprising: a first layer of fibers generally oriented to provide arelatively high tensile strength in a first direction, and at least asecond layer of fibers similar to the first layer and disposed insurface contact therewith and generally oriented In a second directiontransverse to the first direction; whereby the laminated backingprovides the liner with properties including a high tensile strength andsubstantially improved stress properties.
 7. A bearing liner for usebetween a first surface and a second surface for reducing the frictionbetween the first and second surfaces during relative movement betweenthe first and second surfaces, comprising: first means constituting afibrous material and having first and second major surfaces forreinforcing the liner, the first means having characteristics providinga deflection in response to a given compressive force; second means foradhering the first major surface of the first means to the secondsurface; and third means constituting particles of a low frictionmaterial in a mechanically bonded relationship with the fibrous materialconstituting the first means and providing a low friction layer betweenthe first means and the first surface, the third means including anadhesive.
 8. The bearing liner as defined in claim 7, wherein fibers aredisposed at random within the fibrous material.
 9. The bearing liner asdefined in claim 8 wherein the third means includes an intimate mixtureof an adhesive and the particles of the low friction material constitutea powder.
 10. The bearing liner as recited in claim 9 wherein the fiberis a vegetable fiber and the deflection of the liner is substantialydirectly proportional to the applied compressive force.
 11. The bearingliner as defined in claim 10 wherein the vegetable fibers arecompressed.
 12. The bearing liner as defined in claim 10 wherein thevegetable fibers includes rice.
 13. The bearing liner as defined inclaim 9 wherein the first means is formed from at least a pair oflaminations and wherein the fibers are oriented in a first one of thelaminations to provide a relatively high tensile strength in a firstdirection and wherein the fibers are oriented in a second one of thelaminations to provide a relatively high tensile strength in a seconddirection transverse to the first direction.
 14. The liner set forth inclaim 1 wherein the low friction layer extends above the second majorsurface by a dimension no greater than approximately 0.0035 inches. 15.The liner set forth in claim 1 wherein the particles of low frictionmaterial have a thickness no greater than 5 microns and wherein theparticles of low friction material are retained between the fibers ofthe fibrous backing.
 16. The liner set forth in claim 15 wherein theparticles of low friction material constitute a polytetrafluoroethyleneand wherein the polytetrafluoroethylene constitutes approximately 20percent to 35 percent of the low friction layer by weight with theremainder constituting the adhesive.
 17. The liner set forth in claim 16wherein the adhesive in the adhesive layer and the adhesive in the lowfriction layer are the same and wherein the low friction layer extendsabove the second major surface by a distance no greater thanapproximately 0.0035 inches.
 18. A bearing liner as set forth in claiam8 wherein the fibers in the fibrous material are compressed.
 19. Abearing liner as set forth in claim 18 wherein the third meansconstitutes an intimate mixture of an adhesive and the particles of thelow friction material and wherein the low friction material constitutesa polytetrafluoroethylene.
 20. The bearing liner set forth in claim 7,wherein the first means includes fibers disposed within the fibrousmaterial and wherein the first means provides a relatively small amountof deflection when subjected to different compressive forces and furtherprovides substantially a linear relationship between progressive amountsof progressive forces imposed upon the first means and the deflectionproduced in the first means by such progressive forces.
 21. The bearingliner set forth in claim 20 wherein the first means comprises a pair ofatTached laminations each formed from a fibrous material with one of thelayers having fibers disposed in a first orientation and the other layerhaving fibers disposed in a second orientation different from the firstorientation.
 22. The bearing liner set forth in claim 1 wherein thefibrous backing is disposed in layers and wherein the compressed fibershave a first orientation in one of the layers and have in a second oneof the layers a second orientation different from the first orientation.23. The bearing liner set forth in claim 7 wherein the first meansconstitutes at least a pair of layers of the fibrous material andwherein fibers are disposed in a first orientation in one of the layersand wherein fibers are disposed in a second one of the layers in asecond orientation different from the first orientation.